A gas turbine engine includes a turbomachinery core having a high pressure compressor, combustor, and high pressure turbine (“HPT”) in serial flow relationship. The core is operable in a known manner to generate a primary gas flow. The high pressure turbine includes annular arrays (“rows”) of stationary vanes or nozzles that direct the gases exiting the combustor into rotating blades or buckets. Collectively one row of nozzles and one row of blades make up a “stage”. Typically two or more stages are used in serial flow relationship. These components operate in an extremely high temperature environment, and must be cooled by air flow to ensure adequate service life.
Due to operating temperatures within the primary flow path of the gas turbine engine, it may be beneficial to utilize materials with low coefficient of thermal expansion. For example, to operate effectively in such strenuous temperature and pressure conditions, composite materials have been suggested and, in particular for example, ceramic matrix composite (CMC) materials. These low coefficient of thermal expansion materials have higher temperature capability than metallic parts. The higher operating temperatures within the engine result in higher engine efficiency and these materials may be lighter weight than traditionally used metals. However, such ceramic matrix composite (CMC) have mechanical properties that must be considered during the design and application of the CMC. CMC materials have relatively low tensile ductility or low strain to failure when compared to metallic materials. Also, CMC materials have a low coefficient of thermal expansion which differs significantly from metal alloys used as restraining supports or hangers for CMC type materials.
One use for low ductility material is in a turbine shroud. However, various problems are known to exist with shroud hanger assemblies. For example, while CMC may be beneficial for use with shrouds, the hanger may alternatively be formed of metal alloy. Therefore, the issue arises which has heretofore precluded use of low coefficient of thermal expansion materials in combination with metallic, that is how to deal with differential expansion between adjacent components.
Some hanger assemblies have utilized bolts and retainer structures adding components and weights.
It may also be beneficial to ensure that the shroud hanger assembly is properly sealed. Such sealing issues may develop due to thermal growth of parts of differing materials. Such growth may result in gaps between sealing surfaces and may be undesirable. Therefore, a sealing structure is needed due to the differential growth. Such structure also adds weight.
Additionally, the use of multi-piece hanger constructions made of a first material which may differ from the low ductility, low coefficient of thermal expansion second material defining a shroud may also result in air leakage which may be undesirable. It may be beneficial to overcome these and other deficiencies to provide a shroud hanger assembly which provides for sealing of the interfaces between parts of differing material and biases the parts to compensate for differential thermal growth therebetween.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the disclosure is to be bound.